ASD ISM 1821 Ensuring exclusive bundling for TOP SECRET cables
What it says
TOP SECRET cables, when bundled together or run in conduit, are run exclusively in their own individual cable bundle or conduit.
Quoted as published. Everything else on this page is written by Control Stack.
What it means
In plain EnglishTOP SECRET cables must be in separate bundles or conduits to ensure security.
This control is about keeping the communication cables that carry highly sensitive TOP SECRET information separate from others. It means they have their own individual space, so they're safer from eavesdropping or interference. If this isn't done, there's a risk of the information being intercepted or tampered with, which could jeopardise critical operations or national security.
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Why it matters
If TOP SECRET cables share a bundle or conduit with other cabling, electromagnetic or physical access risks could enable compromise or tampering.
How to implement
The IT team should review all existing cable setups to identify any TOP SECRET cables that need separating.
They can do this by checking existing documentation and physically inspecting cable pathways. Update the infrastructure to ensure TOP SECRET cables have their own exclusive bundles or conduits.
Facilities managers should work closely with the IT team when planning new installations to ensure TOP SECRET cables are always routed separately from others.
During planning, use site diagrams to map out cable routes and allocate dedicated paths for sensitive data.
Procurement officers should ensure that any contractors hired for cabling work understand the need for exclusive conduits for TOP SECRET cables.
Include explicit requirements in contracts and discuss them during kick-off meetings with the contractor.
IT security managers should develop a checklist that outlines the separation requirements for TOP SECRET cables.
They should use this checklist during regular inspections to verify ongoing compliance with the control.
Security officers should ensure that all staff are aware of the importance of not mixing cable bundles for different classification levels.
This can be done through regular training sessions, providing examples of what can go wrong if this control is not followed.
Keep it running
Inspect cable routes and conduits to confirm TOP SECRET cabling is in a dedicated bundle/conduit only, with no mixed-classification co-runs.
Evidence and audit
- Check 1 of 5What an auditor asks for
Ask for
A list of all cable routes within the organisation: Request specific layouts and marked pathways for TOP SECRET information cables.
Look at
Separate routes for these cables in diagrams.
Good evidence
Shows each TOP SECRET cable has its own dedicated pathway.
- Check 2 of 5What an auditor asks for
Ask for
The documentation of any installations or changes made to the cabling infrastructure: Check for notes on how this separation was maintained or improved.
Good evidence
Includes records of installations showing exclusive conduits for TOP SECRET cables.
- Check 3 of 5What an auditor asks for
Ask for
The procurement contracts with cabling contractors: Look to ensure they include clauses about exclusive cabling requirements.
Good evidence
Would show contracts specifying requirements for separate conduits for sensitive data.
- Check 4 of 5What an auditor asks for
Ask for
CCTV footage or photographs of cable routes: Verify visually that TOP SECRET cabling is not mixed with other cables.
Good evidence
Includes recent images showing clearly separated cable bundles.
- Check 5 of 5What an auditor asks for
Ask for
To see training records related to this control: Request evidence of staff training on the importance of cable separation.
Good evidence
Would have records of recent sessions explaining why and how to maintain separate pathways.
Mappings
Closest match in ISO/IEC 27001: A.7.12, Secure cabling for power and data, which this control partially meets.
ISO/IEC 27001: 1 mapping
This control partially meets A.7.12.
ISM-1821 requires TOP SECRET cables to be bundled or run in conduit exclusively (i.e., not sharing bundles/conduit with other cables) to reduce the risk of compromise. Annex A 7.12 requires cables carrying power or data to be protected from interception, interference or damage, which can include physical segregation, shielding and routing controls. ISM-1821 is a specific, classification-driven implementation of secure cabling (exclusive bundling) whereas Annex A 7.12 is broader and applies to cabling generally across environments and classifications.
Mappings show how controls relate across frameworks. They do not imply full equivalence or certification.